Decubitus ulcers or pressure sores are areas of damaged soft tissue caused by staying in a single position for a prolonged period of time. They often develop where bones within the body are close to the skin and pressure, or pressure in combination with shear and/or friction, is high. When sufficiently high, these contact forces inhibit blood flow to the contact area. Over time, this obstructed or partially obstructed blood flow can lead to pain, ulceration, osteomyelitis, local infection, and in extreme cases sepsis or death. Other factors, such as malnutrition, skin wetness, and conditions which reduce blood flow or sensation may also play a role.
Compounded on top of this, pressure sore treatment can prove to be very expensive. The average cost associated with a pressure ulcer in the United States was reported to be $48,000 in 2006. This accounts for approximately an 11 billion dollar annual expenditure on pressure ulcer treatment. The severest of pressure sores, categorized as stage IV pressure ulcers, can be even more costly. One study estimated the average cost of such an ulcer to be on average $127,185. Risk of re-injury is also quite high after a previously developed pressure sore has healed or in the process of healing.
Decubitus ulcers are particularly common among populations which have limited mobility. Specifically, according to one study, nearly 40% of those with spinal cord injuries develop pressure ulcers. The true occurrence of pressure ulceration is, however, likely higher because pressure ulcers may be seen as signs of negligent care and are therefore under reported. Additionally, various studies have attributed about 5% of deaths of paraplegics and quadriplegics to complications from pressure sores.
Some methods and strategies for preventing pressure ulcers do exist. Traditional methods of mitigating the risk of pressure sores unfortunately tend to be demanding and disruptive. Generally, traditional methods involve manual repositioning of an individual. This may not be an option for populations with limited or impaired mobility. Another approach for mitigating pressure sore risk is through the use of passive seat cushions which attempt to more evenly distribute pressure across the contacted area of a supported person. Such seat cushions, however, are often still not adequate to prevent pressure sores on their own. Consequentially, such systems may, for example, require a supported person to tilt or recline their seat at predefined intervals to relieve pressure. As such, they are still relatively disruptive. Active cushions also exist which mechanically or pneumatically redistribute or relieve pressure from a desired area. Such cushions are also not without a number of shortcomings. Among these shortcomings, many such pneumatic cushions include interconnected bladders. If one such bladder is compromised, all of the interconnected bladders are compromised as well, and consequentially a person is left uncushioned. In the example of a wheelchair, this may lead to a person being supported only by the hard seat pan which can be injurious to the person, especially as they ride over bumps and are jostled about. The bladders of such seat cushions are not easy or cost effective to replace. These systems also tend to be bulky and may rely on a mobile source of power with limited life.